Might be worth checking to see if they had any spare magazines they might sell... one comment said the UK demill procedure might involve cutting the feed lips off the magazine, but that might be worked around.

I'd read there were some patent disputes between Calico and the Russians. There might be some implementation details to squabble over, but it turns out that rifles with helical magazines were made over 130 years ago.

The Evans Repeating Rifle held 34 cartridges in the buttstock in a helical magazine, with a central rotor and guide strips. It's apparently fairly well known to the old-rifles and cowboy-action guys, but I just now learned of it.

The whole patent thing is something I've read about and basically they designed the Bizon mag similar to the Calico, then when they went to patent it they found the Calico design was already patented, so they redesigned! So I've read...

That's an interesting way to make the guides... a long strip that is wound into one side. Would make things easier to build! That design looks like what Calico uses.

My idea is to use an auger-style rotor to move them with a follower that is hooked onto the auger, forcing it to move when the auger rotates. Sheet metal with an ABS plastic shell. Should work, just need to find a long weekend with nothing else to do but work on it... (yeah right)

[edit]Feeding
One of the Bizon's more unusual features is the magazine, which is often confused for a grenade launcher.[2] The cylinder below the barrel is in fact a 64-round helical magazine, similar to the type used in the American Calico M960 submachine gun.[2] The magazine is made from a durable glass-reinforced polyamide and mounts under the handguard in line with the barrel. This layout makes the weapon more compact and concealable. All cartridges are aligned nose forward in the Bizon magazine and cannot be loaded incorrectly.[2][3] Early magazines were fabricated from aluminium tubing and had a capacity of 67 rounds.[2] The production magazine capacity of 64 was selected as 64 is a multiple of 16, and 9x18mm Makarov rounds are packaged in boxes of 16.[2] The magazine has hooks on top of the front end that engage a pair of pins under the front sight, and the rear end of the magazine interfaces with a Kalashnikov pattern spring-loaded paddle type magazine catch/release located in front of the trigger guard.[6] Some magazines were produced with indicator holes allowing the user to verify the amount of ammunition loaded; these are spaced at 4, 24, 44 and 64-round increments.[3]

If the Wikipedia article is correct and early Bizon magazines were made from aluminum tubing, they'd probably look more like the Evans - smooth on the inside, with a helical guide strip, as opposed to the Calico's molded-in guide strips.

I could see making an aluminum mag by cutting the tube in half and tack-welding in pieces of bent aluminum. The Evans' guide strip must have been cast, as far as I can see. You can't form a strip into a helix like that, as far as I know. It has to be either cast or machined from bar stock.

Moving on to the Calico, I was looking at the pictures Coils posted of the inside of his. I haven't had the cojones to take mine apart yet... anyway, the curved guides mean it's not a simple injection molded part. The guides would keep the part from being removed from the mold since they would wrap around their forming blocks. Looking at the shape, I would guess separate loose blocks assembled into the die, then removed after the part was molded.

That's from my position of ignorance, anyway. If anyone here has any die-making experience, I'd welcome their input.